Spray-dried, mixed metal ziegler catalyst compositions

ABSTRACT

A Ziegler-Natta catalyst composition comprising a solid mixture formed by halogenation of: Al) a spray-dried catalyst precursor comprising the reaction product of a magnesium compound, a non-metallocene titanium compound, and at least one non-metallocene compound of a transition metal other than titanium, with A2) an organoaluminium halide halogenating agent, a method of preparing, precursors for use therein, and olefin polymerization processes using the same.

CROSS-REFERENCE STATEMENT

This application claims the benefit of U.S. Provisional Application No.60/523,616, filed Nov. 20, 2003.

BACKGROUND OF THE INVENTION

The present invention relates to novel spray-dried catalyst compositionsfor use as heterogeneous olefin polymerization catalysts. In particular,the invention provides spray-dried catalyst compositions that arecapable of producing olefin polymers, especially homopolymers ofethylene or copolymers of ethylene and one or more C₃₋₁₀ α-olefins,having a desirable high molecular weight fraction.

Spray-drying techniques have been applied to catalyst compositions, forexample, as an alternative to impregnating the catalyst on a support.For example, U.S. Pat. No. 5,290,745 disclosed preparing a solution oftitanium trichloride and magnesium dichloride in an electron donorcompound (for example, tetrahydrofuran), admixing the solution with afiller, heating the resulting slurry to a temperature as high as theboiling point of the electron donor compound; atomizing the slurry bymeans of a suitable atomizing device to form droplets, and drying thedroplets to form discrete solid, catalyst particles.

It is also known from the teachings of EP-A-449,355, WO93/19100,Research Disclosure 218028-A, and WO93/11166 to prepare particles ofMgCl₂, optionally containing a controlled quantity of residual alcoholby spray drying alcoholic solutions of magnesium dichloride. Theresulting product is used to prepare supported catalysts by contactingwith TiCl₄ or other titanium containing complex forming compounds.

Despite the advances in the art occasioned by the foregoing procedures,the polymer products resulting from the use of the foregoing spray driedcatalyst compositions are often of rather narrow molecular weightdistribution, and/or lacking in a desirable high molecular weightcomponent. In addition, the polymers resulting from use of the foregoingcatalyst lack a highly desirable product uniformity, are often deficientin molecular weight, and generally are formed in limited productivity.

Accordingly, there is an ongoing need for providing spray-dried catalystcompositions that are capable of producing olefin polymers having adesirable portion of high molecular weight component and/or a broadmolecular weight distribution. In particular, there is a continuing needto provide spray-dried catalyst compositions comprising a magnesiumdichloride support and a homogeneous mixture of more than one transitionmetal compound, especially a mixture of titanium- and hafnium chloridecompounds. The compositions and spray-drying methods of the presentinvention satisfy these needs.

SUMMARY OF THE INVENTION

The present invention provides a catalyst precursor composition usefulfor forming solid, Ziegler-Natta catalyst compositions, methods offorming such precursors by means of spray drying, methods of preparingcatalyst compositions from the foregoing catalyst precursorcompositions, and olefin polymerization processes employing theresulting catalyst compositions.

In general, the present invention is directed to a catalyst precursorcomposition comprising the spray-dried reaction product of a magnesiumcompound, a non-metallocene titanium compound, and at least onenon-metallocene compound of a transition metal other than titanium. Theprecursor composition may additionally comprise and preferably doesadditionally comprise a filler material, especially silica. Thepreferred source of such silica filler material is fumed silica which isadded to a solution of the magnesium, titanium and transition metalcompound in the primary diluent prior to spray drying. In a preferredembodiment, the spray-drying process employs as a primary diluent anorganic compound containing hydroxyl functionality, ether functionality,or a mixture thereof.

The catalyst precursor compositions in turn may be converted intoprocatalyst compositions for use in Ziegler-Natta polymerizationprocesses by halogenation of the foregoing precursor composition. In apreferred embodiment, the halogenation agent is an organoaluminum halideor organoboron halide halogenating agent. The resulting procatalyst isrendered active for addition polymerization, especially polymerizationof olefin monomers, by combination with an organoaluminum activatingcocatalyst.

In a highly preferred embodiment, there is provided a Ziegler-Nattaprocatalyst composition comprising a solid mixture formed byhalogenation of:

-   -   A1) a spray-dried catalyst precursor comprising the reaction        product of a magnesium compound, especially magnesium        dichloride, a non-metallocene titanium compound, especially a        titanium chloride compound, and at least one non-metallocene        compound of a transition metal other than titanium, especially a        hafnium compound, with    -   A2) an organoaluminium halide or organoboron halide halogenating        agent.

The invention further provides a process for producing an olefinpolymer, which comprises contacting at least one olefin monomer underpolymerization conditions with a catalyst composition as described aboveand an organoaluminum activating cocatalyst. The resulting polymers areprepared in high productivity and are characterized by broad molecularweight distribution due to formation of at least some high molecularweight polymer. In one embodiment, a “tail” or minor amount of the highmolecular weight component is detectable in a chromatogram of thepolymer. In other embodiments, the amount of high molecular weightcomponent is significant, resulting in a polymer having bimodalmolecular weight distribution. By varying the amount of secondtransition metal, especially hafnium, the quantity of such highmolecular weight component may be varied to produce polymers meetingspecific performance objectives. In addition, catalyst morphology andparticle size are readily controlled, resulting in improved catalysthomogeneity and morphology. This results in higher resin bulk density,improved product conveying properties and reduced product segregation.

Forming a solid catalyst composition by spray drying a homogeneoussolution of suitable metal compounds and halogenating the resultingcatalyst precursor according to the present invention produces catalystparticles having a uniform distribution of active sites and homogeneouschemical composition. The catalyst produces a resin of uniformcomposition in which the high and low molecular weight components areuniformly dispersed, thereby resulting in resins having reduced gels orinhomogeneous fractions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photomicrograph of the catalyst precursor composition ofExample 7.

FIG. 2 is a photomicrograph of the ethylene/1-hexene copolymer of Run 8.

FIG. 3 is a graph of molecular weight distribution (DMWD) as a functionof log Mw for polymers prepared according to runs 1,8 and comparative A.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of United States patent practice, the contents of anypatent, patent application or publication referenced herein is herebyincorporated by reference in its entirety herein, especially withrespect to its disclosure of monomer, oligomer or polymer structures,synthetic techniques and general knowledge in the art If appearingherein, the term “comprising” and derivatives thereof is not intended toexclude the presence of any additional component, step or procedure,whether or not the same is disclosed herein. In order to avoid anydoubt, all compositions claimed herein through use of the term“comprising” may include any additional additive, adjuvant, or compound,unless stated to the contrary. In contrast, the term, “consistingessentially of” if appearing herein, excludes from the scope of anysucceeding recitation any other component, step or procedure, exceptingthose that are not essential to operability. The term “consisting of”,if used, excludes any component, step or procedure not specificallydelineated or listed. The term “or”, unless stated otherwise or apparentfrom the context, refers to the listed members individually as well asin any combination.

The expression “copolymer” (and other terms incorporating this root), asused herein, refers to polymers formed from the polymerization of two ormore comonomers. The expression “catalyst” or “catalyst composition” asused herein refers to transition metal compounds or mixtures thereofthat are useful in causing or effecting the polymerization of additionpolymerizable monomers, generally in combination with one or morecocatalysts or activator compounds. Preferred catalysts are mixtures orcomplexes of non-metallocene transition metal compounds and magnesiumchloride compounds, alternatively referred to as Ziegler-Nattacatalysts. The term “metallocene” refers to organometallic compoundscontaining one or more carbocyclic aromatic or dienyl ligands that arebound to the metal by means of delocalized π-electrons.

More specifically, the present catalyst compositions comprise magnesiumdichloride having supported thereon a mixture of Group 4 metal halides,especially a mixture of titanium chlorides and hafnium chlorides, whichis suitably prepared by spray drying a solution comprising a magnesiumcompound, especially magnesium dichloride, and the mixture of Group 4metal compounds, especially halide containing compounds in a primarydiluent, especially a diluent comprising one or more C₂₋₆ alcohols, andsubsequently halogenating, preferably chlorinating the resulting solidparticles. Preferred transition metal halides are a mixture of titaniumtrichloride (which may be complexed with AlCl₃ if desired) and hafniumtetrachloride. Preferred halogenating agents are organoaluminum halides,especially alkylaluminum sesquichlorides, such as ethylaluminumsesquichloride (Al₂(C₂H₅)₃Cl₃). The relative quantities of magnesiumcompound, transition metal compounds, and halogenating agent employed,as well as the identity of the halogenating agent all affect therelative performance of the resulting catalyst composition.

The molar ratio of magnesium compound to transition metal compounds usedpreferably lies in the range from 0.5/1 to 10/1, and more preferably isfrom 1/1 to 3/1. The molar ratio of titanium compound to hafniumcompound in the preferred catalyst precursor compositions preferablylies in the range from 100/1 to 1/20, and more preferably is from 10/1to 1/10. Most highly preferred catalyst precursors comprise magnesium,titanium and hafnium metals wherein the molar ratio, Mg/Ti/Hf, is x/1/y,where x is a number from 2 to 10, and y is a number from greater than 0to 10. Depending on the desired polymer properties, the range of x and ymay be varied to produce different polymer properties for particular enduses.

Suitable primary diluents used in the spray drying process includeorganic compounds that are capable of dissolving the magnesium compoundand transition metal compounds used in forming the catalyst composition.Especially suited are alcohols, ethers, (poly)alkyleneglycols,(poly)alkyleneglycol ethers, and mixtures thereof. Preferred primarydiluents are C₂₋₁₀ aliphatic alcohols, C₂₋₁₀ dialkylethers, C₄₋₁₀ cyclicethers, and mixtures thereof. A most preferred primary diluent isethanol.

Additional optional components of the composition used to form thespray-dried catalyst precursors include:

B) one or more fillers or bulking agents;

C) one or more internal electron donors; and/or

D) one or more secondary diluent compounds selected from the groupconsisting of siloxanes, polyalkylene glycols, C₁₋₄ alkyl or phenylmono- or diether derivatives of polyalkylene glycols, and crown ethers.

Any solid finely dispersed material that is inert to the othercomponents of the catalyst system and subsequent polymerization, can beemployed as filler or bulking agent for the present compositions.Desirably, the filler provides bulk and strength to the resulting solid,spray-dried particles to prevent particle disintegration upon particleformation and drying. Suitable fillers can be organic or inorganic.Examples include silica, (especially fumed silica), boron nitride,titanium dioxide, zinc oxide, polystyrene, and calcium carbonate. Fumedhydrophobic, surface modified, silica is preferred because it impartshigh viscosity to the slurry and good strength to the spray-driedparticles. The filler should be free of absorbed water and is desirablysurface modified as well. Surface modification, such as silanetreatment, removes reactive hydroxyl or other functional groups from thefiller.

The filler is not utilized to provide an inert support for deposition ofcatalyst composition. Accordingly, materials having high internalporosity are not essential or desired for use. Suitable fillers shouldhave an average particle size (D₅₀) no greater than 50 μm, preferably nogreater than 10 μm. Preferred fillers are aggregates of smaller primaryparticles having a D50 particle size of 0.1-1.0 μm. Examples includefumed silica, such as Cabosil™ 610, available from Cabot Corporation.Sufficient filler is employed to produce a slurry suitable forspray-drying, that is, a mixture including a primary diluent that isliquid at normal atmospheric conditions but readily volatilized underreduced pressure or elevated temperature. Desirably the slurry containssuch filler in an amount of from 0 percent by weight to 15 percent byweight, preferably from 2.5 percent by weight to 10 percent by weight.Upon spray-drying, the resulting droplets produce discrete catalystparticles after evaporation of the primary diluent. Desirably, theamount of filler present in the resulting catalyst particles is anamount from 0 to 50 percent, preferably from 10 to 30 percent based ontotal composition weight. The spray-dried catalyst particles produced inthis manner typically have D50 particle size of from 5-200 μm,preferably from 10-30 μm.

Secondary diluent compounds may be employed to prepare spray-driedproducts exhibiting particular properties such as uniform particle size,particle sphericity, improved catalyst activity, and reduced fines.Preferred polyallylene glycol secondary diluents include polyethyleneglycol, containing from 2 to 5 alkyleneoxide repeat units. Siloxanes andcrown ethers are particularly preferred secondary diluents because theycan provide improvements in particle morphology as well as increasedactivity in comparison to polymerization reactions conducted without thepresence of such siloxane or crown ether compound. Preferred siloxanesinclude hexamethyldisiloxane, hexaethyldisiloxane andhexaphenyldisiloxane. Preferred crown ethers include 18-crown-6-etherand 15-crown-5-ether. The secondary diluent is preferably present in thecatalyst composition in an amount in the range of from 0.5 to 10 percentbased on total catalyst composition weight.

Additional optional ingredients in the composition to be spray driedinclude antistatic agents, emulsifiers, and processing aids which areknown to be useful in the art of spray drying to prevent particleagglomeration or fractionation.

Spray-drying may be affected by any spray-drying method known in theart. One example of a suitable spraydrying method comprises atomizingthe catalyst composition optionally with heating, and drying theresulting droplets. Atomization is accomplished by means of any suitableatomizing device to form discrete droplets that upon drying formspherical or nearly spherical shaped particles. Atomization ispreferably effected by passing a slurry of the catalyst compositionthrough the atomizing device together with an inert drying gas, that is,a gas which is nonreactive under the conditions employed duringatomization and aids in removal of volatile components. An atomizingnozzle or a centrifugal high speed disc can be employed to effectatomization, whereby a spray or dispersion of droplets of the mixture isformed. The volumetric flow of drying gas, if used, preferablyconsiderably exceeds the volumetric flow of the slurry to effectatomization of the slurry and/or evaporation of the liquid medium.Ordinarily the drying gas is heated to a temperature as high as 160° C.to facilitate atomization and drying of the slurry; however, if thevolumetric flow of drying gas is maintained at a very high level, it ispossible to employ lower temperatures. Atomization pressures of from1-200 psig (100- 1.4 MPa) are suitable. Alternately, reduced pressure inthe spray recovery section of the dryer can be employed to effect solidparticle formation. Some examples of suitable spray-drying methodssuitable for use with the present catalyst composition include thosedisclosed in U.S. Pat. No. 5,290,745, U.S. Pat. No. 5,652,314, U.S. Pat.No. 4,376,062, U.S. Pat. No. 4,728,705, U.S. Pat. No. 5,604,172, U.S.Pat. No. 5,306,350, U.S. Pat. No. 4,638,029, and U.S. Pat. No.5,716,558.

By adjusting the size of the orifices of the atomizer or the speed ofthe centrifical high speed disk employed during spray-drying, it ispossible to obtain particles having desired average particle size, forexample, from 5-200 μm.

The spray dried solid precursor is recovered and halogenated with anorganoaluminum halide in order to form an active complex of themagnesium and transition metal halides. The identity and quantity of thehalogenating agent employed is selected to result in a catalystcomposition having the desired performance properties. A particularlypreferred halogenating agent is ethylaluminum sesquichloride. Thehalogenation agent is employed in molar quantities based on hafniumcompound from 1/1 to 10/1, preferably from 1.5/1 to 2.5/1. At higherratios of halogenating agent, catalyst productivity is adverselyaffected. At lower ratios of halogenating agent polymer molecular weightdistribution (Mw/Mn) is too narrow.

Halogenation is conducted according to conventional techniques.Preferably the solid precursor particles are suspended or slurried in aninert liquid medium, usually an aliphatic or aromatic hydrocarbonliquid, most preferably one or more C₅₋₅₀ hydrocarbons, such as hexaneor mineral oil. The halogenation agent is then added to the mixture andallowed to react with the precursor for a time from 1 minute to 1 day.Thereafter the solid particles are optionally rinsed free from unreactedhalogenated agent and dried or maintained in a liquid medium until use.

Formation of olefin polymers is achieved by contacting one or moreaddition polymerizable olefin monomers with the catalyst composition andan activating cocatalyst, especially an organoaluminum compound,especially a trialkylaluminum compound. Preferred cocatalysts includetriethyl aluminum, triisobutyl aluminum and tri-n-hexyl aluminum. Theactivating cocatalyst is generally employed in a range based on moles ofcocatalyst:moles of transition metal compound of from 2:1 to 100,000:1,preferably in the range of from 5:1 to 10,000:1, and most preferably inthe range of from 5:1 to 100:1.

In formulating the catalyst composition, it is preferred that theco-catalyst be separately added to the reactor contents, to the recyclestream of the reactor, or to the monomer or monomers charged to thereactor, and not incorporated into the catalyst particles per se.

The catalyst composition may be used for any reaction for whichZiegler-Natta type polymerization catalysts are normally useful,especially suspension, solution, slurry and gas phase polymerizations ofolefins. Such reactions can be carried out using known equipment andreaction conditions, and are not limited to any specific type ofreaction system. Such polymerization can be conducted in a batchwisemode, a continuous mode, or any combination thereof. Generally, suitableolefin polymerization temperatures are in the range of from 0-200° C. atatmospheric, subatmospheric, or superatmospheric pressures up to 10 MPa.It is generally preferred to use the catalyst compositions inpolymerizations at concentrations sufficient to provide at least0.000001, preferably 0.00001 percent, by weight, of transition metalbased on the weight of the monomers to be polymerized. The upper limitof the percentages is determined by a combination of catalyst activityand process economics.

Preferably, gas phase polymerization is employed, at superatmosphericpressure in the range of from 1-1000 psi (7 kPa-7 MPa) at temperaturesin the range of from 30-130° C. Stirred or fluidized bed gas phasereaction systems are particularly useful. Generally, a conventional gasphase, fluidized bed process is conducted by passing a stream containingone or more olefin monomers continuously through a fluidized bed reactorunder reaction conditions sufficient to polymerize the monomer(s) and inthe presence of an effective amount of catalyst composition and anactivating cocatalyst at a velocity sufficient to maintain a bed ofsolid particles in a suspended condition. A stream containing unreactedmonomer is withdrawn from the reactor continuously, compressed, cooled,optionally fully or partially condensed as disclosed in U.S. Pat. No.4,543,399, U.S. Pat. No. 4,588,790, U.S. Pat. No. 5,352,749 and U.S.Pat. No. 5,462,999, and recycled to the reactor. Product is withdrawnfrom the reactor and make-up monomer is added to the recycle stream. Inaddition, a fluidization aid such as carbon black, silica, clay, or talcmay be used, as disclosed in U.S. Pat. No. 4,994,534. Suitable gas phasereaction systems are also described in U.S. Pat. No. 5,527,752.

Slurry or solution polymerization processes may utilize subatmosphericor superatmospheric pressures and temperatures in the range of from40-110° C. Useful liquid phase polymerization reaction systems are knownin the art, for example, as described in U.S. Pat. No. 3,324,095, U.S.Pat. No. 5,453,471, U.S. Pat. No. 5,527,752, U.S. Pat. No. 5,834,571, WO96/04322 and WO 96/04323. Liquid phase reaction systems generallycomprise a reactor vessel to which olefin monomer, catalyst compositionand cocatalyst are added, and which contains a liquid reaction mediumfor dissolving or suspending the polyolefin. The liquid reaction mediummay consist of the bulk liquid monomer or an inert liquid hydrocarbonthat is nonreactive under the polymerization conditions employed.Although such an inert liquid hydrocarbon need not function as a solventfor the catalyst composition or the polymer obtained by the process, itusually serves as solvent for the monomers employed in thepolymerization. Among the inert liquid hydrocarbons typically used forthis purpose are C₃₋₈ alkanes, such as propane, butane, iso-butane,isopentane, hexane, cyclohexane, heptane, benzene, and toluene. Reactivecontact between the olefin monomer and the catalyst composition shouldbe maintained by constant stirring or agitation. Preferably, reactionmedium containing the olefin polymer product and unreacted olefinmonomer is withdrawn continuously from the reactor. Olefin polymerproduct is separated, and unreacted olefin monomer is recycled into thereactor.

The catalysts of the current invention are capable of producing olefinpolymers over a wide range of molecular weights, where the molecularweight distribution is characterized by a high molecular weight tailextending into the 10⁶ to 10⁷ molecular weight range. The high molecularweight component is uniformly blended at the molecular level with thelower molecular weight component. Such resins are difficult if notimpossible to obtain by means of a post-reactor melt blending process.The additional high molecular weight polymer tail resulting from use ofthe catalyst compositions of the invention desirably increases the meltstrength of the resin among other benefits. As previously mentioned, theratio of the various metal components of the catalyst may be variedwithin the previously disclosed range to produce polyolefin productswith specifically desired physically properties suited for particularend uses.

More particularly, catalyst precursors having a metal molar ratio,Mg/Ti/Hf_(y), where x is a number from 1 to 6, preferably from 3 to 5and y is a number from 2 to 5, preferably from 2 to 4 are especiallysuited for preparation of high molecular weight polyolefins, especiallyethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene resins. Suchresins are highly desirable for use in sheet and film applications.

Catalyst compositions according to the present invention having a metalmolar ratio, Mg,/Ti/Hf_(y), where x is a number from 3 to 8, preferablyfrom 4 to 7, most preferably 5, and y is a number from 0.1 to 1.2,preferably from 0.2 to 1.0 are highly desirable for producing olefinpolymers having properties suited for stretch tape and monofilamentapplications. Such resins have melt indices from 0.5 to 5 and Mw/Mn ofgreater than 5.0. The catalysts for use in this application also possesshigh catalyst productivity and good hydrogen chain transfer response.

These catalysts containing relatively high Mg content and moderate orlow levels of Hf are also especially useful when employed in two-stagepolymerizations such as those disclosed in U.S. Pat. Nos. 5,589,539,5,405,901 and 6,248,831. The catalyst compositions can be used to obtainethylene/α-olefin resins of broadened or multimodal molecular weightdistribution, wherein the amount of comonomer incorporated into thepolymer in each reactor is independently controllable. Such processesrequire a catalyst composition capable of producing a very highmolecular weight polymer in one reactor, and a low molecular weightpolymer in a second reactor. The catalyst thus must be able to produceresin at very high propagation/chain termination ratios in one reactor,and much lower propagation/chain termination ratios in the secondreactor. The resulting polymers having extremely high melt strength areuseful for manufacture of cast sheet and pipe products.

The catalyst compositions are characterized by a lack of undesirablesmall (1 μm or less) particulate residues that normally result duringpreparation of catalyst compositions impregnated on porous silicasupports. The presence of these residues in the resulting polymerinterferes with certain applications such as filament spinning. Suchresidues are difficult to economically remove from the polymer via meltscreening or similar post reactor technique.

It is expressly intended that the foregoing disclosure of preferred ordesired, more preferred or more desired, highly preferred or highlydesired, or most preferred or most desired substituents, ranges, enduses, processes, or combinations with respect to any one of theembodiments of the invention is applicable as well to any other of thepreceding or succeeding embodiments of the invention, independently ofthe identity of any other specific substituent, range, use, process, orcombination.

It is understood that the present invention is operable in the absenceof any component which has not been specifically disclosed. Unlessotherwise stated, implicit from the context or conventional in the art,all parts and percentages herein are based on weight.

EXAMPLES

The following examples are provided in order to further illustrate theinvention and are not to be construed as limiting. The term “overnight”,if used, refers to a time of approximately 16-18 hours, “roomtemperature”, if used, refers to a temperature of about 20-25° C. Allsyntheses and manipulations of air-sensitive materials were carried outin an inert atmosphere (nitrogen or argon) glove box.

Preparation of Spray Dried Catalyst A Precursor (Molar RatioMg/Ti/Hf=3/1/2)

Magnesium dichloride (6.41 g), 4.40 g of TiCl₃.⅓ AlCl₃, and 13.2 g ofHfCl₄ are placed into an oven-dried, 500 ml, three-neck round bottomflask. Anhydrous ethanol (200 ml) is then added to the flask, the flaskis placed in an oil bath set at 100° C., and the flask contents refluxedfor 3 hours resulting in the formation of a clear, blue colored reactionmixture. The solution is cooled to room temperature. 8.92 g of fumedsilica that has a silane surface treatment (Cab-O-Sil™ TS-610, availablefrom Cabot Corporation) is weighed into an oven-dried 500 ml bottle, andthe bottle is sealed with a septum. The bottle is purged with nitrogenfor approximately 30 minutes, and then the cooled solution from theflask is transferred to the bottle. The bottle is placed on a rolleruntil the solution and silica are thoroughly mixed. The resultingmixture is spray-dried under nitrogen atmosphere, and the dry powder isrecovered and stored under inert conditions.

Preparation of Spray Dried Catalyst B Precursor (Molar RatioMg/Ti/Hf=5/1/4)

Magnesium dichloride (4.77 g), 2.05 g of TiCl₃.⅓ AlCl₃, and 16.1 g ofHfCl₄ are placed into an oven-dried, 500 ml, three-neck round bottomflask. Anhydrous ethanol (200 ml) is then added to the flask, the flaskis placed in an oil bath set at 100° C., and the flask contents refluxedfor 3 hours resulting in the formation of a clear, blue colored reactionmixture. The solution is cooled to room temperature. 8.80 g of fumedsilica that has a silane surface treatment (Cab-O-Sil™ TS-610, availablefrom Cabot Corporation) is weighed into an oven-dried 500 ml bottle, andthe bottle is sealed with a septum. The bottle is purged with nitrogenfor approximately 30 minutes, and then the cooled solution from theflask is transferred to the bottle. The bottle is placed on a rolleruntil the solution and silica are thoroughly mixed. The resultingmixture is spray-dried under nitrogen atmosphere, and the dry powder isrecovered and stored under inert conditions.

Examples 1-3

Within the confines of a dry-box, 10.0 g of spray dried precursor A areplaced into an oven-dried, 500 ml, three-neck round bottom flaskequipped with a stir bar. The sealed flask is then removed from thedrybox, and fitted with a nitrogen line, condenser and an additionfunnel. Hexane (100 ml) is added to make a slurry. Using the additionfunnel while the flask is cooled in an ice bath, 2.5 (Ex. 1), 5 (Ex. 2)or 10 (Ex. 3) equivalents of a 25 percent hexane solution ofethylaluminum sesquichloride (EASC) are added dropwise to the flaskresulting in formation of a dark brown composition accompanied by slightwarming of the mixture (5° C.). The flask is placed in an oil bath setat 90° C., and the flask contents refluxed for 2 hours. Stirring isdiscontinued, the flask is removed from the oil bath, and the flaskcontents cooled to room temperature. The solid product is allowed tosettle to the bottom of the flask, and the supernatant is removed bydecantation, washed three times with hexane (50 ml) and dried underreduced pressure.

Examples 4-6

Precursor B (1.40 g, 0.75 mmole Ti) is placed into an oven-dried, 20 mlglass, crimp-top vial equipped with a stir bar. Mineral oil (4 ml)(Kaydol™ oil available from Witco Corporation) is added to the vial, andthe vial is sealed. The vial is then removed from the dry-box andconnected to a nitrogen line. EASC, 1.3 equivalents (Ex. 4), 3.4equivalents (Ex. 5) or 5 equivalents (Ex. 6) is then slowly added to thevial. The vial is then placed in a 65° C. oil bath and heated for 2hours. The vial is then removed from the oil bath, cooled to roomtemperature and stored under an inert atmosphere.

Slurry Polymerization

A 1 liter stirred autoclave reactor is charged with 500 ml hexane, 10 ml1-hexene, and triisobutylaluminum (TiBA) in an amount sufficient toprovide about 1000: 1 molar ratio based on Ti, and sufficient catalyst/mineral oil slurry to give a charge of from 0.5-1.0 micromoles of thecatalysts prepared in Examples 1-6. The reactor temperature is raised to60° C. and the reactor allowed to equilibrate. Ethylene is fed tomaintain a reactor pressure of 1 MPa, the catalyst is charged bypressure injection and the reactor temperature controlled at 85° C.After 30 minutes reaction time, ethylene feed is stopped, the reactor iscooled and vented, and the polymer recovered and evaluated. Meltrheological properties of the polymers are tested according to ASTMD-1238.

Results are contained in Table 1. TABLE 1 Mg/ Run Catalyst Ti/Hf EASC/HfProductivity¹ FI² I₂₁/I₅ Mw/Mn 1 Ex. 1 3/1/2 2.5 12,000 8.7 11 5.3 2 Ex.2 ″ 5.0 8,500 9.7 23 12 3 Ex. 3 ″ 10.0 6,500 6.7 23 13 4³ Ex. 4 5/1/41.8 4,900 8.6 31 5.2 5³ Ex. 5 ″ 3.4 7,000 13 91 9.1 6³ Ex. 6 ″ 5.0 2,8002.5 — 16 7³ Ex. 6 ″ ″ 2,600 15.8 250  —¹g PE/g cat/hr/690 kPa ethylene²flow index, dg/min, ASTM D-1238, condition F (21 kg)³Runs 4, 5, 6 and 7 included hydrogen at molar ratios H₂/C₂H₅ of 0.3,0.3, 0.6 and 1.1 respectively

The data in Table 1 illustrate that polymer properties, includingmolecular weight and molecular weight distribution as well as catalystproductivity are affected by the precursor's Mg/Ti/Hf molar ratio aswell as the quantity of alkylaluminum halide compound (EASC) employed inthe halogenation process. In particular, higher EASC/Hf ratios result ina broader MWD. At the same EASC/Hf ratio, the higher quantities of Hf inthe catalyst precursor results in production of a resin with a lower FI,which indicates the formation of a higher molecular weight polymer.Consequently, the hafnium component appears to be responsible forpreparing the higher molecular eight polymer component of the polymer.

Example 7

Preparation of Spray Dried Catalyst C Precursor (Molar RatioMg/Ti/Hf=5/1/1)

A solution containing 17.6 kg ethanol, 540.3 g TiCl₃(AcAc), 886 ganhydrous MgCl₂, 592 g HfCl₄ is prepared by stirring the foregoingcomponents for 3 hours. Fumed silica filler (1880 g, Cabosil™ TS-610) isadded, and the slurry spray dried in a rotary wheel spray-drier at 15kg/hr slurry feed, inlet temperature 160° C., outlet temperature 106° C.Analysis (mmol/g): 0.5 Ti, 2.3 Mg, 0.48 Hf, 6.62 Cl, 4.89ethanol/ethoxide (Mg/Ti/Hf=5/1/1). Freely flowing, spherical particlesof average particle size 22.5 micrometers, particle size distribution(span) of 1.3 are obtained. BET surface area is 32.9 m²/g. Single pointBET pore volume is 0.16 cc/g. A photomicrograph of the precursorparticles is shown in FIG. 1.

The precursor is chlorinated in mineral oil at a Cl/OEt molar ratio of2. Accordingly, 12 g of precursor C is slurried in 40 g of mineral oil,and treated at room temperature with three portions of 10 g each of 30percent ethyl aluminum sesquichloride. The reaction is initiallyexothermic. The resulting slurry, optionally further diluted withmineral oil is used directly for preparation of ethylene/ 1-hexenecopolymers.

An aliquot of the slurry is washed several times with hexane, and dried.SEM analysis indicates that the spherical morphology of the precursorparticles is maintained. BET surface area of the resulting catalystcomposition is 123 m²/g. Single point BET pore volume is 0.31 cm³/g.

The slurry polymerization conditions of runs 1-7 are substantiallyrepeated, excepting that the Al/Ti ratio in the reactor is maintained at10-25:1, and 5 ml of 1-hexene comonomer are used. The cocatalystsemployed are triethyl aluminum (TEAL), triisobutyl aluminum (TIBAL) andtri-n-hexyl aluminum (TNHAL). Results are contained in Table 2. TABLE 2C₂ partial H₂/C₂ pressure, Run Cocat. Al/Ti Ratio psi (kPa) Prod.¹ MI²FI³ I₂₁/I₂ Mw/Mn⁴ 8 TEAL 10 0.38 95 (660) 11,200 0.6 27 45 7.05 9 TIBAL″ 0.36 96 (660) 13,000 0.5 28 54 11.4 10 TNHAL 25 0.53 85 (590) 8,2003.1 111 36 7.4 11 TIBAL 10 0 10 (70)  15,000 — <.3 — 12 TIBAL ″ 0 30(210) 15,500 — <.3 — — 13 TEAL 20 2.1 100 (690)  4,500 28 840 30 9.0¹Productivity, g PE/g cat/hr/690 kPa ethylene²melt index, dg/min, ASTM D-1238, condition E (2.1 kg)³flow index, dg/min, ASTM D-1238, condition F (21 kg)⁴Standard Reference Material 1496, available from National Institute ofstandards and Technology, is employed as a calibration standard

Resin bulk densities range from 0.3-0.4 g/cc. The polymer particlesessentially replicate the shape and size distribution of the catalystprecursor. A photomicrograph of the polymer from run 8 is shown in FIG.2.

Comparative A

A comparative catalyst precursor, substantially identical to catalystprecursor C of Example 7 but lacking hafnium is prepared. The Mg/Ti/Hfmolar ratio is 5/1/0. The precursor is halogenated substantiallyaccording to the technique of Example 7, recovered and employed toprepare ethylene/1-hexene copolymers under conditions analogous to thoseemployed for runs 1-13. The product does not contain an enhancedquantity of high molecular weight fraction, as evidenced by reference toFIG. 3, which is a graph of molecular weight distribution (DMWD) as afunction of log Mw for polymer prepared according to runs 1, 8 andcomparative A.

Examples 8 and 9

A catalyst composition according to Example 7 is employed in a two stagepolymerization process to prepare an ethylene/1-hexene copolymersubstantially as disclosed in U.S. Pat. No. 5,405,901. The resultingtwo-stage resin has a very broad molecular weight distribution comparedto single-stage resins due to the wide difference in molecular weightsof the two components. Excellent catalyst productivity is obtained atgood resin bulk density and low resin fines production. Typical resinproperties are shown in the following table. Example 8 Example 9Conditions 1^(st) stage 2^(nd) stage product 1^(st) stage 2^(nd) stageproduct Temperature ° C. 75 100 80 100 C₂H₄ Partial Pressure (kPa) 345725 341 725 H₂/C₂H₄ Molar Ratio 0.12 1.6 0.07 1.6 Hexene/ethylene MolarRatio 0.04 0.0 0.04 0.0 Production Rate (kg/hr) 9.9 9.3 14.7 7.3 BedWeight (kg) 58.0 44.0 57.7 44.1 Residence Time (hr) 5.8 2.3 3.9 2.0 FlowIndex, I21 (dg · min) 0.27 14.7 0.53 6.9 Melt Index, I2 (dg/min) 0.120.06 Melt Flow Ratio (I21/I2) 151.8 102.6 Density (g/cm³) 0.9266 0.950.9261 0.944 Titanium (ppmw) 5.6 2.4 3.3 1.8 Bulk Density (kg/M) 381 436327 386 D50 (mm) 0.7 0.8 0.8 0.8 Fines (percent <120 mesh) 1.2 0.9 1.10.8 Compositional split (percent) 42 58 54 46

1. A Ziegler-Natta catalyst precursor composition comprising thespray-dried reaction product of a magnesium compound, a non-metallocenetitanium compound, and at least one non-metallocene compound of atransition metal other than titanium.
 2. The precursor composition ofclaim 1 additionally comprising a filler.
 3. The precursor compositionof claim 2 wherein the filler is silica.
 4. A process for preparing aZiegler-Natta precursor composition comprising forming a solution of amagnesium, titanium and transition metal compound in a primary diluentand spray drying the liquid composition to form solid particles of theprecursor composition.
 5. The process of claim 4 wherein the primarydiluent comprises an organic compound containing hydroxyl functionality,ether functionality, or a mixture of hydroxyl and ether functionality.6. A process for conversion of a catalyst precursor composition into aprocatalyst composition for use in Ziegler-Natta polymerizationprocesses comprising halogenating a precursor composition according toclaim
 1. 7. A process according to claim 6 wherein the halogenatingagent comprises an organoaluminum halide halogenating agent, anorganoboron halide halogenating agent, or a mixture thereof.
 8. Acatalyst composition comprising a solid mixture formed by halogenationof: A1) a spray-dried catalyst precursor comprising the reaction productof a magnesium compound, a non-metallocene titanium compound, and atleast one non-metallocene compound of a transition metal other thantitanium, with A2) a halogenating agent comprising an organoaluminiumhalide, and organoboron halide, or a mixture thereof.
 9. The catalystcomposition of claim 8 wherein the spray dried catalyst precursorfurther comprises at least one filler.
 10. The catalyst composition ofclaim 8 wherein the filler is surface modified fumed silica.
 11. Thecatalyst composition of claim 8 wherein the precursor comprisesmagnesium, titanium, and hafnium.
 12. The catalyst composition of claim8 wherein the molar ratio Mg/Ti/Hf in the catalyst precursor is x/1/y,where x is a number from 2 to 10, and y is a number from greater than 0to
 10. 13. The catalyst composition of claim 8 wherein the halogenatingagent comprises ethylaluminum sesquichloride.
 14. A process for forminga Ziegler-Natta catalyst composition according to claim 8 comprisinghalogenating: A1) a spray-dried catalyst precursor comprising thereaction product of a magnesium compound, a non-metallocene titaniumcompound, and at least one non-metallocene compound of a transitionmetal other than titanium, with A2) a halogenating agent comprising anorganoaluminium halide, an organoboron halide or a mixture thereof. 15.An olefin polymerization process comprising contacting one or more C₂₋₂₀olefins under polymerization conditions with a catalyst compositionaccording to any of claims 8-13 or prepared according to the process ofclaim 14 and an organoaluminum activating cocatalyst.
 16. A processaccording to claim 15 wherein the cocatalyst is triethylaluminum.